This disclosure relates to medical articles, and more particularly to wound dressings and medical tapes for use on skin and wounds. Wound dressings and tapes may need to adhere to a variety of skin types and remain effective in the presence of various amounts of moisture, whether a low exuding wound, a high exuding wound, or a patient that is diaphoretic. In all of these circumstances, the wound dressing or tape is desirably able to respond to dynamic levels of moisture present to ensure adequate wear time. Modifications to medical articles to improve permeability to moisture are known and include, for example, selectively or pattern coating an adhesive onto a permeable film surface or creating new adhesives with higher moisture permeability. Examples of selective adhesive coating may include a continuous polymeric thin film having a pressure sensitive adhesive (PSA) that is selectively coated on one surface of the polymeric thin film such that 40 to 75 percent of the film surface does not contain adhesive. Moisture is preferably transmitted through the areas without adhesive.
While the pattern or selective coating may result in medical articles with higher moisture transmission rates, pattern coated adhesive in certain situations can have poor edge adhesion, resulting in edge lift. The methods and equipment used to pattern coat an adhesive can be more expensive and elaborate than the methods and equipment used for coating the adhesive in a continuous film-type manner. In addition, the methods and equipment can be quite specialized for a particular adhesive system and not interchangeable between different adhesive systems.
Methods of creating different adhesive properties are also known, and include adding additives to PSA copolymers. Plasticizers, humectants, inorganic salts, organic salts, or microcolloids may be added to a pressure sensitive adhesive to enhance breathability and make the adhesive suitable for medical articles. Such compounds are fully mixed in and/or dispersed throughout the adhesive prior to construction of a medical article. Thus, the adhesive composition as a whole is made more permeable to moisture by uniform dispersion or mixing of hydrophilic materials. In many cases these uniformly mixed or dispersed additives can significantly change the properties of the adhesive properties throughout the adhesive, especially in the presence of high moisture conditions.